The mechanisms by which oral streptococci interact with teeth, saliva, and with each other to form cariogenic dental plaque are under investigation. Adsorption of S. mutans and/or S. sanguis to hydroxyapatite surfaces does not require sucrose whereas plaque formation by S. mutans on smooth surfaces such as glass appears to involve the formation of adherent glucans from sucrose. Treatment of hydroxyapatite with calcium ions, human saliva, cariostatic agents, or lipoteichoic acid modulates the adsorption of streptococcal cells. Results imply a role of lipoteichoic acid in adsorption of streptococci to hydroxyapatite. Cariostatic agents (e.g.bis-biguanides) which inhibit microbial growth are also potent inhibitors of cell-associated glucan synthesis and adherence to glass. Antibodies to glucosyltransferases and dextranases also prevent S. mutans adherence to glass, but do not effect growth or acid production.